The present disclosure herein relates to a memory device and method for manufacturing a memory device, and more particularly, to a method for manufacturing a flash memory device having improved reliability.
Flash memory devices are devices capable of electrically erasing and programming data and preserving data when power is not supplied. Thus, demand for flash memory devices is increasing in various fields.
Such a flash memory device may be classified into a floating gate-type flash memory device and a charge trap-type flash memory device according to a kind of a memory storage layer which constitutes a unit cell.
The floating gate-type flash memory device may have a stacked gate structure including a floating gate formed by disposing a tunnel oxide layer and a control gate stacked by disposing a dielectric on the floating gate. The flash memory device having the above-described structure may increase a threshold voltage of a memory cell through a programming process in which electric charges are injected into the floating gate or decrease the threshold voltage of the memory cell through an erasing process in which electric charges are discharged from the floating gate to a semiconductor substrate. Thus, a flash memory device may read data from the memory cell using the variation of the threshold voltage.
When the flash memory device performs programming and erasing operations, since the electric charges are injected or discharged into/from the floating gate through the tunnel oxide layer, reliability of the flash memory device may be significantly affected by characteristics of the tunnel oxide layer. Also, the tunnel oxide layer may be damaged by dry etching and cleaning processes during the manufacture of the flash memory device. Thus, the characteristics of the tunnel oxide layer may be degraded to reduce the reliability of the flash memory device.